The overall objective of this project is to examine the relationship between gene structure and expression during development. The specific approach is to examine the structure and expression of the actin multigene family in the sea urchin, Strongylocentrotus purpuratus. The complete nucleotide sequence of two different cloned sea urchin actin genes is being determined. Additionally, the size and relative abundance of the actin mRNA, at selected stages of development is being examined by RNA blot analysis. It is hoped that properties of the actin genes, as revealed by sequencing might ultimately by correlated with the control of their expression during development.